Venice, a city intricately woven with waterways and historic architecture, faces a profound challenge as water levels persistently rise. This unique urban landscape, celebrated globally for its heritage, is increasingly vulnerable to the encroaching sea. The interaction of natural geological processes and broader environmental changes contributes to a complex situation threatening its future.
Factors Contributing to Rising Waters
Venice’s vulnerability stems from a combination of natural land subsidence and global sea-level rise. The city is built upon a dynamic lagoon environment, where the underlying sediments naturally compact over time, causing the land to gradually sink. This geological process, known as subsidence, has historically contributed to the city’s descent at rates ranging from 0.5 to 2 millimeters per year. Additionally, the slow movement of the Adriatic tectonic plate, which subducts beneath the Apennine Mountains, also causes the city’s elevation to subtly decrease.
Compounding this natural sinking is the accelerating rise in global sea levels. This phenomenon is primarily driven by two factors linked to climate change: the thermal expansion of ocean water as it warms and the melting of glaciers and ice sheets worldwide. As ocean temperatures increase, water molecules expand, occupying more volume, while meltwater from continental ice masses directly increases total ocean volume. These combined effects mean that Venice is not only sinking but also experiencing a simultaneous increase in the surrounding sea height, exacerbating the water level challenge.
Current Flooding Reality
Rising water levels lead to frequent “Acqua Alta,” or high water events, which regularly inundate parts of the city. These events are common between late September and April, peaking in November and December. During an Acqua Alta, low-lying areas, notably Piazza San Marco, are among the first to flood, often requiring temporary elevated walkways for pedestrian movement.
While these high tides typically last for a few hours, receding with the natural tidal cycle, their increasing frequency and severity disrupt daily life, transportation, and local businesses. Public water transport routes may be modified or suspended, and shops sometimes close to prevent damage. Beyond inconvenience, prolonged exposure to saltwater accelerates the decay of Venice’s historic infrastructure, affecting building foundations and damaging intricate mosaics, frescoes, and stone facades. The 2019 floods, for instance, saw over 80% of the city submerged, causing extensive damage to cultural sites, including more than 50 churches and the thousand-year-old crypt under St. Mark’s Basilica.
Future Submergence Projections
Scientific models project increasingly severe and potentially permanent inundation for Venice. Recent studies indicate that tidal levels in the Venetian lagoon are rising at an average rate of approximately half a centimeter per year. Without additional protective interventions, parts of Venice could be permanently underwater by 2150. Areas like Piazza San Marco could be submerged under 70 centimeters of water.
Projections for relative sea-level rise in Venice vary depending on future emission scenarios. By 2100, estimates range from an increase of 17 to 120 centimeters. More detailed scenarios for 2150 suggest a rise of about 35 to 55 centimeters under optimistic emission reduction efforts, but potentially exceeding 120 centimeters in a high-emission future without mitigation. These projections indicate Venice could face widespread, permanent submersion, fundamentally altering its landscape and habitability.
Protective Measures
In response to the escalating threat, Venice has implemented MOSE (Modulo Sperimentale Elettromeccanico). This system uses 78 mobile gates at the three main inlets connecting the Venetian Lagoon to the Adriatic Sea: Lido, Malamocco, and Chioggia. When high tides are predicted to reach a certain threshold (typically 110 to 130 centimeters), compressed air is pumped into the hollow gates, causing them to pivot upwards from the seabed, forming a temporary barrier.
The MOSE system was first activated in October 2020, successfully preventing flooding in low-lying areas like Piazza San Marco. The gates can be raised in 30 minutes and lowered in 15, with operation based on tide forecasts. Beyond MOSE, other measures include raising pavements and improving drainage systems to mitigate less severe high water events.